The type-I allergic response is a complicated immune reaction induced by release of granules containing histamine and serotonin through cross-linking of high affinity IgE receptors mainly expressed in the mast cell and basophilic leukocytes with IgE antibodies and allergens. This reaction has been elucidated to be composed of the following three stages:    A) An initial stage including production of cytokines such as IL-4 and IL-5 from T cell by stimulation of allergens, production of the IgE antibody from B cell, and differentiation and proliferation of the mast cells induced by production of the cytokines;    B) An intermediate stage from cross-linking of Fcε receptors by the IgE antibody and allergen to degranulation of the mast cell; and    C) A later stage such as enhanced vascular permeability by histamine and serotonin after degranulation.
The inventors of the present invention have isolated an adapter molecule BASH that is specifically expressed in B cell (J. Immunol., 161:5804–5808, 1998). This BASH has a similar molecular structure to SLP-76 (J. Biol. Chem., 270:7029–7032, 1995) that is expressed in T cell, and indicates the presence of a family of signal transducers specific to hemopoietic immunoreceptors through structural and functional analysis.
While suppression of IgE antibody production (Primary Stage) by B cell using a hyposentitization therapy, or suppression of the later stage by administration of anti-histaminic agent have been used today for treating allergies, neither of them serves as an effective therapy in the current situations.
A part of the molecular mechanism of the type-I allergy response is being made clear, on the other hand, as described above. However, the signal transduction mechanism involved in degranulation of mast cell through the high affinity IgE receptor has not been known yet. It is inevitable to elucidate the molecule involved in the degranulation process of mast cell not only for elucidating the molecular mechanism of the allergy response but also for developing therapeutic methods or therapeutic agents of the allergic diseases. Particularly, since the mast cell plays a critical role in expression of the allergic conditions, the signal transducer that is specifically expressed in mast cell is quite important for developing novel antiallergic agents that selectively block the Fcε receptor signal transduction system that causes the degranulation reaction involving release of histamine and serotonin.
The object of the present invention performed based on the foregoing situations is to provide signal transducers specifically expressed in mouse and human mast cells, and polynucleotides (cDNAs) encoding these protein molecules.
Another object of the present invention is to provide various genetic engineering materials involved in the signal transducers.